Method of and apparatus for operating electric motors.



W. SIEBENMORGBN.

METHOD OF AND APPARATUS FOR OPERATING ELECTRIC MOTORS.

APPLICATION FILED JULY 31,1909.

1,101,214, Patented June 23,1914.

(r fe/W14 m. M A a COLUMBIA Pumomunm cm, WASNINGTDN. n. c

UNITED sTA rns I PATENT OFFICE,

WILLIAM SIEBENMORGEN, OF WESTFIELD, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO C. 8; C. ELECTRIC & MANUFACTURING COMPANY, A CORPO RATION OF NEW JERSEY.

METHOD AND APPARATUS FOR OPERATING ELECTRIC MOTORS.

Patented June 23, 1914.

Application filed July 31, 1909. Serial No. 510,587;

To all whom it may concern 2 Be it known that I, WILLIAM. SIEBENMO-R- mm, a citizen of the United States, residing at \Vestfield, New- Jersey, have inventedcertain new and useful- Improvements in Methods of and Apparatus for Operating Electric Motors, of which the following is a clear, full, and exact description. 8

My invention relates to a method of and apparatus for operating'electric motors, and my object is to improve-on the methods and onstructions heretofore used.

' In order to obtain a wide range-of-speed or power with two motors which drive the same load, it has been common to provide two motors 'and to operate them iii-series for the lower speeds and in parallel for the higher speeds, and to obtain intermediate speeds mainly by the introduction of external resistances in the armature circuit-s. Such methods of control are, however, open to many objections both on account of the waste of power entailed in the use of large ohmic resistances, and the impossibility of obtaining a great range of speed without a great waste of power. I

Various constructions and methods liave been proposed to obviatesome of the foregoing objections, among which may be-mentioned the following patents: 690,810, 690,807, 734,724, 747,236, 557,185, 743,601, 573,979, 517,948,-444,900. In some of said patents it has been proposed to use motors whose armatures develop different counter electromotive forces at the same speeds or same relative speeds, such as by providing one of the armatures with a greater number of turns than the'other, but each one of them has inherent defects which are overcome by my .invention.

In the drawings which show a preferred embodiment, Figure 1 shows diagrammatically the different connections made by thecontroller shown in Fig. 2, and Fig. 2 is an embodiment of controller for causing those connections.

In carrying out my invention I have provided two motors, which are preferably shunt-wound, and whose rotors (preferablythe armatures) are mechanically connected or coupled, such as by being geared to the same load, so that their rotors revolveat-the same speed ratio at whatever speed the load is driven. The armatures develop different J 1 counterv electromotive forces at the same speed of the load, and this is preferably accomplished byproviding. one 90f. the armatures "with a greater: number of turns than the othergarmature. As-it is preferable to have both motors alike or substantially alike in size, I may correspondingly decrease the s ze, of the-wireinthe armature of the one which has the-greaternumber ofturns, ,I,n-a,imotor, where .we;-as .'T-[

counter electromotive force,- mthe, number of revolutions per second, Z' the number of con-iductors in ser es on. the armature counted .by the, two armatures Will be equal,. to--.tl1e

sum of their counter relectromotive-iforces,

and therefore if we postseribe 1 ,to each value of one motor and 2 to eachvalue of the other motor, in order to indicate which motor any particular value-belongs to, E (total counter electromotive force) 1 but as n n" the'equation may be writ-ten +E 1 from which i+Ez Y n=mfiiearlyp and the revolutions per minute If thefields (N and N) are-alike and Z is greater than Z E and IE will increase number of turns Were-operated independently at that speed. The-speed at which a .all aroundthe-pe'rfliphery, and the strength ,11101301 operated alone. will run varies nearly inversely as the strength of thefield. fore from the above equation;

Therea decrease in N will result in-a greater com-.1

to E times Ca, where Cai sthecurriit in t'lii': The armature current is equal arnia-ture. I to the f'dltfige its'ann'stnr e-terminals mince irs czsanuer entertainer-refere both being (evicted by t'he iesisfiance ofthe arm'a tan; erreuit: Byche -"f0ninri;i:. ,Z; N a de i-eiiseiginwtne field s rength 'win at that instm wesere glue speed riseswdecr'ease the eennreh 'eleen amefi ve fierce-anti; allow a greater uni-ear as new eheat-gm the {1111i}?!- u re, tries eitertrrlg a'greeter corqfie or pcwer,

wiisimeasewhe ween e-r ramioh nins in 1mm inertesifigw-E (an-d ester-"ready detreatin new mail n istsam te the verse-gt stressnse t nel-antithesis egs or same filidssesanrewaedny ewe-fi s; em n the ass efiwew meeees ihgennnenfjr coa'piea- 1:0- getlfiiiffiitli ileir'srnaeuree series and mxnngnemsesme "streiigtif but with e e -et er (A?) -1 the field reagentsn wiIf iri'eresetaepea',.- and miss le-teasenew FE ma; n ar til: their tl1 irhi5fress-d eletrdmbtw force me iilterillfllessee Wiueaeh- :inererse in seat-n w enema; ear ier, sine strength field, B will decrease-inn iri'i is'be- 7 a decreaseillspeed remains the same) increase the power, or (by-equation l fis iiii (Z N )+(Z=N. \Villlllerease the speed if the lbad isfn'ot e 'snr-ea. 3* *neeseweneps iii decrease fthe gout-liter efieetrdmdcve' force and fididiet of iiialifi h rdfleedto zero, thus gradii'zilly iii'ci eii sltig-th sfjed or the apparatus and gradually transferring the work done, Eiiid counter electronictive 'rfdrce developed;

clone or horse power that motor hating circuit may be iibt'ained b1 \i'iliding A with many turns compared with A so that even with full strength in both fields at start, the counter electromotive force dereloped by A \\'lll nearl reach the sum at the slowest speed fore give a slow initial running speed, while the coi'nparatirely few turns on A will, after A is 'i'einored from the circuit, enable the operator to still further increase the speed' of the apparatus much beyond that possible with the two when in series, and: this too by merely reducing". the' field of A i'n a This is importantsimilar manner. in driving apparatus wherea steady} increase ofispeedwithout a ny jerks is desired,- 's'uch 2lS'll1' Vb printing presses and other apparatus; for minute graduations' -in field strength are easily obtainable; The: foregoing principles areparticularly ap'p'lica ble'to' the caseof shunt-wound motors,"in which the shnht'field-windingis usually a great number of turns of fine wire. The greatest range of speed of asingle shunt motor alone, which is obtainable by field control solely is about 1 to 6, that is, if the" impressed voltage across its armature terminals is not changed and it runs at for example revoliitions per minute with full strength field','its speed can be increased.

I by field" reduction solely, to only aboutGOO R; 1?; M. The same isvtrue if two shuntmotors exactly alike are coupled together.--

- W'itli' tivto shunt wound motors, mechanicall)? connected together so as to rotate at the same-speed ratio, with. their afmatures connected in series so that the current through each is substantially t-he'sam and whose armatures have a great difference in the number of turns; the range of speedmay be giea'tlyincreased, as will be obvious from the foregoing explanation. 'tiiely large number. of turns on the slow speed armature enablesthe apparatus to run at a very slow initial speed, as of course the torque .is correspondingly great on account of the larger number. of turns, and the motors may be made the same size if the size of the Wire in the slowspeed armahire is correspondingly reduced.- Of course the size should besufiicient to properly carry the current. which it may be called; upon to conduct. The counter electromoti've force developed by the slow speed armature is of coin-sej irrespective of the size of the wire, and the same principles would apply even though t e 'wire were of the same. size as thatzin the high speed armature, but this would entail an increase in the size of the slow .spe'ed motor which would be objectiona'ble in most-cases. '[t is therefore pref- The com'paraerable to decrease the size of the wire in the slow speed armature.

Referring now to the drawings which show an exampleof my method of control, A is the armature and 3 the shunt field of the slow speed motor, and A the armature and 4 the shunt field of the high speed motor. The armatures are connected in se rles. The two rotors (m this case the armatures) are mechanically connected or coupled together such as by being geared to the same load S as indicated in Fig. 2, so as to rotate at the same speed ratio.- This ratio may be 1 to 1 if the gears are of the samestrength untilthe slowspeed motor. is cut out. 1 This may not benecessary; in all cases. The .slow speed armatureA is wound with more turns than: the high speed armature A, and willtherefore ,do -most of. the work at the initial slow speed; 4

5 is a starting'resistance, used merely to prevent a too ,great rush of currentuntil it can be'taken careof by the counter electromotive forcedeveloped, which is cut out to bring the apparatus up to the initial slow speed which is represented in Diagram 2. i

- Inv orderto reducethe strength ofthe field 3 to gradually?increase.the speed, a resistance 6 may begradually inserted in the field circuit if desired; the afield-then shunted through-theiresistance 7, and the resistance gradually cut 1 :out, as shown in iDiagram 5, thusgradually bringing the' field strength substantially to zero, after which the field may be cutout as shown in Diagram 6 leaving armature A running free and developing no counter electromotive force, or substantially none. The shunt field circuit may then be opened (first inserting a resistance 7 as shown in Diagram 7, if desired) leaving the circuit as shown at 8, after which the armature A may be shunted (through a resistance 9 and the resistance cutout as shown at 10 if desired) and the armature then disconnected as shown in the position 11. Diagrams 6-8-are transitory positions, as they do not affect the current in the armature circuit. The apparatus will then be driven by the high speed motor alone, with its field 4 at full strength and will then be running at its slowest individual running speed. The speed may then be further increased-by reducing the field strength of the high speed motor, for example by gradually inserting a resistance 6 in the field circuit. It will be obvious that I do notdesire to limit myself to the particular steps or method of weakening the fields which have been illustrated, as this may be accomplished in various ways.

In order to show the wide difference between my method of control and that possible by field control only where a single independent shunt wound motor is used, the speed range ratio obtained by field control solely in one independent shunt-wound motor or two motors which are alike and coupled together, is only about 1 to 6, yet with two motors the turns on whose armatures'difi'er and which are controlled in the manner heretofore explained, I may obtain any speed range ratio desired up to l to 42, or even higher, that is, if the two motors are designed to run at an initial slow speed of say lOO revolutions per minute when in series as-indicated in Diagram 2 of Fig.1, I may, by field control solely, gradually increase the speed, until by the high speed motor; alone the. speed will reach, 4200 .or even higher. The 'diflerence. in the X number of turns necessary upon the two armatures will'partly depend upon the ratio between the initial slow speed and the highest speed. Roughly this maybe taken as one to the square root-of the higher number of the ratio between the lowest initial speed with full strength fields and maximum impressed electromotive force, and the highest speed of the high speed motor used alone and with its field weakened ,to the greatest extent. Forexample, if the apparatus is desired to be run at an initial'slow speed of 100 with both motors, and at 2000 by the high speed motor alone, the number of turns on the slow speed armature may be to the number of turns on the high speed armature as somewhat less than the square root of 20 (say 4) is to 1. This, however, should not be taken as an invariable ratio, because it maybe considerably varied depending upon the conditions confronting the designer, If, for example, it were desired to have the speed range ratio 1 to 20 as before but it were not desired to run for long periods on the slow speeds, but only on the higher speeds, the ratio of the number of turns might be increased to, for example, 5 to l; and vice versa, if it were desired to run for long periods on the slow speeds the ratio might be 3 to 1, for example.

Of course the maximum strength of the fields, and the number of turns on the two armatures, and the gradations of field reduction necessary, would depend on the particular work to be done. It will be obvious to any one skilled in the art that if an electrician is to design the machine to operate with a given load at a given slow speed and to obtain the speed range ratio which he may desire, it would, after the foregoing explanations, be a mere question of calculation from known electrical formula, in view the. particular conditions he Wishes'to' obtain, in order to obtain that result. Therefore no detailedexplanation of ,such calculations need be' here-insertedfor this would be ap arentto designers skilled in the art.

(If course while I h'aly'e' ex'plained' my 'll'iet-h'od with particular reference to only two motors; it may as Well be adapted to [tions' being th'at the 'additional motor 01- ha -eta be taken into consid- Iii-Fig.2 r time s'liown'a controller ivhich may be'usedfo'r obtaining the connections elnd thother blocks and bars are stationary.

Wherl tlie moviii j briishreaches the posit-i o n dotted-dine 1-,- the'circui ts shown "in 1' of Fig. re closed,and as the cated by dotted lines; 2 to 12; the" changes i he the c i reli its ihdicated by 11 the Dia rams 2 to'lE 'il is 'the initial terlihl i'e-'silstallce re ni'o tied from the arm any il'l beobtainfdfi Positio run in speedwith all eitt'nre (iii-e it As the-controller removed farslrr m the rightg' itfiwilh gradually redhpe "m ht be use theifcu't itTOiit, and thereafter ncrease the the liih gpbed "motor to its m axiw l'iz'l't l olz'17im"is: 1 1*: Theli 'tl'iotl of operating tw'o motors by Sate-eerie mpswhile: their arniature's are elect-1 ma lly connected in" series", whose rotors {ire mechaniba-llycoupled-so as to rotate at thesamef s eed ragtioand w'hose arma'tures dei elopd-i tl'erent counter lectr'omotiye forces at the same relatii'e'speetEwvhieh consists" in gradually redueinfi -tosnbstantially zero the field. strength oft-liesl'oiv speed-motor While lfuiintaining-said series connection said nech'anical'eouplingf: I

2. The method of increasing the speed of a high speed and asl-ow s'peed motor by successive steps while their armatuies' are electrically connected'in series, whose" rotors are meclia'nically coupled so asto rotate at the same speed ratio and whose armatures 1' cessive steps While their armatures are elect'ri'cally connected in series, \vho'se rotors are mechanically coupled so as to rotate at the same speed ratio and Whose armatures develop different counter electromotive' forces at the same relative speed; which consists in gradually reducing to substantially z'erothe field strength of the slow speed motor while maintaining said series connection and said mechanical coupling and without materially reducingthe armature current, and then cut-- tingout the slow speed armature:

'l he method of increasing thespeed of a high'speed and as'low speed motor by Suecessive steps while their armatures are'electri'ca'lly connected in series, whose rotors are mechanically coupled so as to rotate at the saline sjieed ratio and whose armatures develop difl rent counter electrolnotive forces at the's'a in'e relative sp'ee'd' which consists in gradually reducingto substantially zero the field strength of the slow speed motor While maintaining said series connection and said mechanical coupling and Without materially reducing the armature current, thenj cutting out the slow speed armature, and operating the load by gradually reducing the field strength of the high speed motor.-

7 5. The method of operating two shuntwound motors by succ'es'sivestepsWhile their a'rmatures are electrically connected in series, whose rotors are mechanically con"- pled so as to rotate at the same speed ratio, the" turns on the armatures of which difier in number; which consists in' gradu'ajlly reducing to substantially 'zero the fie'l'd strength ofithat motor Whose armature has the greater number of turns while "maintain i'ng said series connection and withbut materially reducing the armature" current, then shunting and cutting out said armature, and thereafter increasing the speed bygfldually reducing the field strength'of the other motor. 1

6. The method of gradually increasing the sum of the powers of two motorsby s'uc eessive steps while their a-rm'aturesare' connected in series so that substantially all the current through one armature also passes through the other whose rotors are mechanically coupled so as to rotate" zit the same speed ratio and whose armatures develop different counter electrornotive' forces at the same relative speed" which consists in gradually reducing to substantially zero the counter electrom'otive' force of the slow speed motor by gradually reducing the field strength of the same, while substantially maintaining the armature current and while maintaining said series connection and said mechanical coupling.

7. The metliod' ofincreasing the" slim of the p'owexs of twd' motors by 's'ucces'sii'e's'te'ps while their armatures are directly connected inser'ies so that substantially all the current through one armature also passes through the other, whose rotors are mechanically coupled so as to rotate at the same speed ratio and whose armatures develop difierent counter electromotive forces at the same relative speed, which consists in gradually reducing the counter electromotive force of the slow speed motor by gradually reducing the field strength of the same, without materially reducing the armature current and while maintaining said series connection, continuing such reduction of said field until the armature is substantially dead, shunting the same, cutting out said armature and further increasing the power by reducing the field strength of the other motor.

S. The method of operatingtw'o' motors while their armatures are electrically connected in series, whose rotors are mechanically coupled so as to rotate at thejsame speed ratio and whose armatures have a different number of .turns,;:which; consists in increasing the speed by successive steps each step comprising weakeningthe fieldot that motor which has the greaterhumber of turns in such a way as-to cause a temporary increase of current through both armatures,

thereby increasingithe s eed, and continuing such steps until the fiel of said motor is re-.-

duced to substantially zero.

9. The method of operating two motors while their armatures are electrically con nected in series, Whose rotors are mechanically coupled so as to rotate at the same speed ratio and whose armatures have a different number of turns, which consists in increasing the speed by successive steps, each step comprising weakening the field of that motor which has the greater number of turns in such a way as to cause a temporary increase of current through both armatures, thereby increasing the speed, continuing said steps until the counter electromotive force of said armature is reduced substantially to zero, then cutting out said armature and operating the apparatus by the other motor.

10. The method of operating two motors having shunt field windings, whose rotors are mechanically coupled together so that one drives the other. and the turns on whose armatures materially differ in number and whose armatures are in series so that substantially the same current passes through each, which consists in gradually reducing to substantially zero the counter electromotive force of that armature which has the greater number of turns by gradually reducing its field strength without reducing the combined power of the two motors, cutting out said armature, and gradually reducing the field strength of the other motor.

11, The method of operating two shuntwound motors whose rotors are mechanically coupled together so that one drives the other, and the turns on whose armatures materially differ in number and whose strength of the other motor.

12. The method of operating two shuntwound motors whose rotors are mechanically coupled together so that one drives the other, and the turns on whose armatures materially difier in number and whose armatures are in'series so that substantially the same current passes through each, which consists in gradually reducing to substantially zero, 'by field variation alone, the

counter electromotive force of that armature which has the greater number of turns,- shunting said armature by a connection in series with the other armature,cutting the former armature out, and graduallyreducing the field strength of the other motor."

. 13. Two motors whose armatures have a difi'erent'number of turns-and are' electri cally connected in series so that substantially all the current of each also passes through the other, a mechanical connection between the rotors of said motors whereby they rotate at the same speed ratio, in combination with a controller adapted to gradually reduce to substantially zero the field strength of that armature which has the greater number of turns and thereafter cut out said armature.

14. Two shunt motors whose armatures have a different number of turns and are electrically connected in series so that substantially all the current of each also passes through the other, a. mechanical connection between the rotors of said motors whereby they rotate at the same speed ratio, in combination with a controller adapted to gradually reduce to substantially zero the field strength of that arn'iature which has the greater number of turns and thereafter cut out said armature.

15. Two motors whose armatures have a different number of turns and are electrically connected in series so that substantially all the current of each also passes through the other, a mechanical connection between the rotors of said motors whereby they rotate at the same speed ratio, in combination with a controller adapted to gradually reduce to substantially zero the field strength of that armature which has the greater number of turns and thereafter cut out said armature, said controller being also provided with mechanism and connections to thereafter gradually reduce the field strength of the other motor.

16. Two motors whose armatures have a 09ml; a mm l h le maint ning the; rgtqns mgghanlcally coupLed and the arma- 18. @116 method 0i ingjreasing the Qped ahfihq am l t v p whi c nsis i Cally couplqd ind the; armgmhires c n ect'eqL i 1 1 sgrigs, and Lhgargaflgen varying. the speed of; the gthe r mptpn by reducing its field mngbht Sig ed; qr N. Y., ew Qf July, 99

WIEEIAM. SWEENMQBGEN this 28th 

